Why Pain Can Flare After a Nerve Block

A nerve block can bring welcome numbness in the first hours—and then a frustrating rise in pain once that numbness fades. For many people, that flare is temporary and does not mean the procedure failed. This article explains why it happens, how common it is in published studies, and when to call for help. It is general education, not personal medical advice.

GSMC physicians, including Dr. Dharam Mann, perform image-guided nerve blocks and related injections for patients seen in Toms River (1314 Hooper Ave), Freehold (322 Professional View Dr), and West Long Branch (100 NJ-36), as well as our other offices. GSMC has several physicians. Dr. Mann personally performs spinal cord stimulation, MILD, Intracept, and InterStim when those options are later appropriate. InterStim implants are done at Manchester Surgery Center; consults are offered at all locations.

For a step-by-step recovery overview, see our earlier guide, What to Expect After a Nerve Block. Related reading: how long an epidural steroid injection may last and selective nerve root blocks.

Two medicines, two timelines

Many nerve blocks use a local anesthetic, often with a corticosteroid. Those medicines do not peak at the same time:

• The anesthetic can ease pain within minutes. That effect usually fades over a few hours (sometimes up to about a day, depending on the medicine used).
• A steroid, when used, is meant to calm inflammation. It often takes days, not hours, to help.

In the gap between those two effects, your usual pain can return—or feel sharper, especially if the injection site is sore. That pattern is common after injections that combine a numbing medicine and a steroid.

In a 2023 prospective study of ultrasound-guided musculoskeletal corticosteroid injections, about one in five patients (20.7%) reported a post-injection pain flare. Among those who later improved, 60.4% noticed relief within three days, and 93.7% within a week. That study was not limited to spinal nerve blocks, so the exact percentages may not match every spine procedure, but the timing is consistent with what many patients describe.

What a “steroid flare” is

A flare is a short-lived increase in pain after a corticosteroid injection. Older and more recent injection studies put the chance in a fairly wide band, often about one in five to about one in three patients, depending on the joint or tendon treated and how a flare was defined:

• Extra-articular hand and wrist injections (trigger finger and de Quervain’s): a 2007 randomized study found a flare—defined as a rise of two or more points on a pain scale—in 33% of patients. Pain often rebounded by the next day and then eased over about a week.
• Shoulder steroid injections: a 2017 cohort reported a flare in 35.3% of patients, lasting a mean of 3.9 days (range one to seven days).

These papers describe musculoskeletal and extra-articular injections, not every type of spinal nerve block. We cite them because they are careful, published measurements of a well-known steroid effect—not because every nerve block will behave exactly the same way. A flare usually settles in a few days. It is not, by itself, a sign that the injection cannot still help once the steroid begins to work.

If the block was mainly a diagnostic test

When a medial branch block or other diagnostic nerve block uses local anesthetic (with or without steroid), the point of the visit is often to see whether numbing a specific nerve eases your usual pain. When the numb feeling wears off, the pain may come right back. That return can be expected. It does not automatically mean something went wrong, and it is useful information for deciding whether radiofrequency ablation or another step is appropriate. Keep any pain diary you were given.

What may help while you wait

• Follow the written after-care instructions from your procedure team.
• An ice pack on the sore area for 15 to 20 minutes at a time may help, unless you were told not to use ice.
• Take only the pain medicines your clinician has already approved. Do not start, stop, or increase medicines on your own.
• Rest the day of the procedure. Short walks are often fine; avoid driving while a limb is numb, and avoid heavy lifting until you are told it is safe.
• If you have diabetes, check blood sugar more often for a day or two; steroids can raise it temporarily.

When a flare is not the explanation — call promptly

Seek urgent or emergency care, or call 911, for:

• Fever, chills, or increasing redness, warmth, or drainage at the injection site
• New or worsening weakness, or a leg or arm that will not bear weight after the expected numbness should have worn off
• Loss of bowel or bladder control, or new numbness in the groin or saddle area
• A severe headache, chest pain, or trouble breathing
• Pain that keeps getting worse after several days rather than easing, or pain that is far out of proportion to what you were told to expect

Those warning signs are uncommon, but they are not something to “wait out” as a typical flare. When in doubt, call the office: 732-202-3000.

Talk with the team in Toms River, Freehold, or West Long Branch

If you have questions about a recent block, or you are deciding whether a nerve block is the right next step, we can review your history and imaging with you. Request a visit at gsmedicalcenter.org/appointment or call 732-202-3000. Coverage varies. We verify benefits before scheduling procedures.

Sources

1. Cushman DM, Kobayashi JK, Wheelwright JC, et al. Prospective evaluation of pain flares and time until pain relief following musculoskeletal corticosteroid injections. Sports Health. 2023;15(2):227-233. PMC 9950997.
2. Goldfarb CA, Gelberman RH, McKeon K, Chia B, Boyer MI. Extra-articular steroid injection: early patient response and the incidence of flare reaction. J Hand Surg Am. 2007;32(10):1513-1520. PMID: 18070637.
3. Fawi HMT, et al. The incidence of flare reaction and short-term outcome following steroid injection in the shoulder. Shoulder Elbow. 2017. PMID: 28588659. PMC 5444605.

This article is for general patient education and is not a substitute for medical advice from your own clinician. Individual results vary.

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